Cylinder block assembly with increased lubricant capacity

ABSTRACT

In an internal combustion engine, a large volume of lubricant is desirable to increase service intervals and thus reduce maintenance costs. Large lubricant volumes typically require an undesirable increase in engine size. A cylinder block assembly for an internal combustion engine in accordance with this invention comprises a cylinder block, a primary lubricant reservoir or sump below the cylinder block, and a secondary lubricant reservoir at a side of the cylinder block. The secondary lubricant reservoir may be formed as a pannier oil tank by sealably attaching an apron to a side of the cylinder block. A fluid passage extending between the secondary lubricant reservoir and the primary lubricant reservoir is closeable by a valve and is adapted to permit lubricant flow from the secondary lubricant reservoir to the primary lubricant reservoir when open. The secondary lubricant reservoir increases the oil capacity of the cylinder block.

TECHNICAL FIELD

[0001] This invention relates to a cylinder block assembly for an engine having an increased lubricant capacity and in particular to a cylinder block assembly in which the volume and flow rate of lubricant within the engine is controlled. The invention also relates to a method of lubricating an engine.

BACKGROUND

[0002] During operation of an engine, a lubricant such as engine oil is pumped from a sump into the working portions of an engine in order to lubricate, clean and cool the engine's moving parts. Excess oil supplied to the moving parts is drained back to the sump along various paths defined in the engine cylinder block and cylinder head.

[0003] A large volume of lubricating oil is desirable in an engine. For example, where the volume of engine oil is increased, service intervals can be increased thereby minimizing maintenance costs. However, the volume of oil that can be employed in an engine is limited by engine size as, in general, it is desirable to maintain engine size at a minimum while large volumes of oil require large storage reservoirs in an engine.

[0004] UK Patent specification No 100,345 describes a lubricating system for a car engine comprising a circulating oil tank located beneath a cylinder block of the engine, and a fresh oil tank formed in the side of the block. Filling of the fresh oil tank results in overflow oil passing through a weir to the circulating oil tank. The system includes a first pump to pump oil from the circulating oil tank to the oil circulation system and a second pump which supplies oil from the fresh oil tank to the oil circulation system. While the fresh oil tank provides an extra volume of oil for the engine, the means for supplying the fresh oil to the circulation system necessitates the use of a pump in the supply line as the disposition of the line is such that oil will not flow to the circulating system when the line is open. Moreover, in order for fresh oil to be supplied to the oil circulation system, both pumps need to operate at the same time. These shortcomings result in a lubricating system which is more expensive to manufacture and operate. The present invention sets out to overcome one or more of the disadvantages of the prior art.

SUMMARY OF THE INVENTION

[0005] According to the invention there is provided a cylinder block assembly comprising a cylinder block, a primary lubricant reservoir below the cylinder block, a secondary lubricant reservoir at a side of the cylinder block, a fluid passage extending between the primary and secondary lubricant reservoirs, and a valve which can be actuated to open and close the fluid passage, wherein the fluid passage is adapted to permit gravitational flow of the lubricant from the secondary lubricant reservoir to the primary lubricant reservoir when open, wherein actuation of the valve is controlled by a level of lubricant in the primary lubricant reservoir.

[0006] The invention also extends to an engine having such a cylinder block assembly.

[0007] The invention also extends to a method for lubricating an engine comprising the steps of:

[0008] pumping lubricant around the engine from the primary lubricant reservoir;

[0009] collecting a proportion of returned lubricant in the secondary lubricant reservoir; and

[0010] controlling the return of lubricant from the secondary lubricant reservoir through the fluid passage to the primary lubricant reservoir by means of the valve.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Various embodiments of the invention will now be described, by way of example only, having regard to the accompanying diagrammatic drawings in which:

[0012]FIG. 1a is a partial transverse cross section through a cylinder block assembly according to one embodiment of the invention, including a cylinder block provided with a secondary lubricant reservoir at a side wall thereof, the cylinder block also being provided with a primary lubricant reservoir and a cylinder head; and

[0013]FIG. 1b is a partial transverse cross section through a cylinder block assembly according to another embodiment of the invention, including a cylinder block provided with a secondary lubricant reservoir at a side wall thereof in which the pannier oil tank is defined by the cylinder block and a cylinder block apron.

DETAILED DESCRIPTION

[0014] A cylinder block 1 is provided with at least one secondary lubricant reservoir which acts as an engine oil capacitor to increase engine lubricating oil capacity. In the present example, the secondary lubricant reservoir takes the form of a pannier oil tank 11; however the secondary lubricant reservoir can be of any construction that may be adapted by a skilled person in accordance with the present invention.

[0015] In FIG. 1a, the pannier oil tank 11 is integrally formed in the cylinder block 1 while in FIG. 1b the pannier oil tank 11 is defined between the cylinder block 1 and a cylinder block apron 2. The illustrated embodiments are described in more detail below, but it is to be understood that the form and construction of the pannier oil tank may be varied in accordance with the present invention.

[0016] As shown in FIG. 1a, the cylinder block 1 is a casting made up of a cylinder block body 4 and a cylinder block base 5. Two cylinder block side walls 35 and two cylinder block end walls 36 upstand from the cylinder block base 5 (only one side wall 35 and end wall 36 is shown). The cylinder block 1 is provided with a primary oil reservoir in the form of a sump 37 attached to the cylinder block base 5. The cylinder block 1 has a cylinder head 8 fitted with a cylinder head cover 9.

[0017] The side walls 35 are shaped to define a crankcase housing 7 of a crankcase 6 adjacent the cylinder block base 5. A crankshaft 10 is contained within the crankcase 6.

[0018] The side wall 35 of the cylinder block 1 is formed to define the pannier oil tank 11 between a side wall outer wall 12 and a side wall inner wall 13 adjacent the cylinder block base 5. The pannier oil tank 11 is further defined by a bottom wall 14 at the cylinder block base 5. A bottom wall valve opening 15 in the bottom wall 14 provides a fluid passage 38 between the pannier oil tank 11 and the sump 37. The pannier oil tank 11 is open at a top end 34. The bottom wall 14 may be formed as a separate plate to facilitate core sand removal from the pannier oil tank 11 where the pannier oil tank 11 is cast integrally with the cylinder block 1.

[0019] The pannier oil tank 11 is adapted to store lubricating oil 16 or other lubricant. The bottom wall valve opening 15 is openable and closeable by a float valve 17 located in the sump 37. The float valve 17 is of substantially conventional construction and is provided with a valve head 18 moveable between an open position to allow drainage of oil 16 from the pannier oil tank 11 through the fluid passage 38 and into the sump 37, and a closed position to allow filling of the pannier oil tank 11 in accordance with oil levels in the sump 37. The bottom wall valve opening 15 is dimensioned to allow relatively brisk oil flow in the open position. As the lubricant level in the sump 37 increases, the valve 17 closes the aperture 15 when the level of the lubricant 16 reaches a predetermined level.

[0020] At its open top end 34, the pannier oil tank 11 is adapted to receive lubricating oil 16 through a filler tube 19 defined in the side wall outer wall 12. Whilst the float valve 17 is in the open position, oil received via the filler tube 19 will pass through the pannier oil tank 11 and through the valve opening 15 into the sump 37. When the oil level in the sump 37 has reached a predetermined design level, the float valve 17 will close the valve opening 15 and the pannier oil tank 11 will commence to fill.

[0021] A conventional dipstick (not shown) or sight glass 40 is used in conjunction with the pannier oil tank 11 to determine when the design quantity of oil has been reached. It is envisaged that the maximum oil level of the engine will be at or just below the open top end 34 of the filler tube 19.

[0022] When the engine is in operation, oil is received in the pannier oil tank 11 from a cylinder block duct 21 which extends between the cylinder head 8 and the pannier oil tank 11 via a cavity 20. The cylinder block duct 21 is located in the cylinder block side wall 35.

[0023] The apparatus may be configured such that the pannier oil tank 11 is the prime recipient of oil from the various oil return sources in an engine. Those sources may include, for example, a pressure relief valve 24, shown in FIG. 1b, that may be required to relieve oil pressure in the lubricating oil circuit of the engine, particularly at low engine speeds.

[0024] It may be found desirable to include, in an engine, more than one float valve 17 or even a series of float valves 17, to cater for the variable engine inclinations that the engine may experience in use. The speed of oil drain from the pannier oil tank 11 into the sump 37 that may be required in use or in service may also influence the number and location of float valves 17.

[0025] The side wall inner wall 13 is provided with an aperture 32 located at the top end 34 of the pannier oil tank 11. The aperture 32 serves as an overflow for the pannier oil tank 11 so that oil can flow from the pannier oil tank 11, through the aperture 32, into the sump 37 when the capacity of the pannier oil tank 11 is exceeded.

[0026]FIG. 1b shows an engine including a cylinder block 1 with a pannier oil tank 11 in accordance with a second embodiment of the invention. The cylinder block 1 of FIG. 1b is broadly similar to the cylinder block 1 of FIG. 1a. Accordingly, like numerals indicate like parts. However, in the present embodiment, the pannier oil tank 11 is defined by an apron 2 and the cylinder block side wall 35. More particularly, the pannier oil tank 11 is defined between the crankcase housing 7 and the apron 2.

[0027] The apron 2 is sealably adhered to the side wall 35 to define the pannier oil tank 11. Briefly, the apron 2 is made up of an apron bottom portion 26, an apron cylinder block portion 27 and an apron cylinder head portion 28 attachable to the cylinder head 8. The apron 2 is formed from a metal sheet or other suitable material and is shaped and contoured to complement the side wall 35 of the cylinder block 1. Advantage is thus taken of a natural cavity that exists in the necked region of a conventional crankcase to define, with apron 2, a pannier oil tank 11.

[0028] The apron 2 is folded at the bottom portion 26 to define an elongate box-like beam 30 for reinforcing the apron 2 and the cylinder block 1 to which the apron 2 is adhered. The beam 30 is secured to a cylinder block flange 31 defined at the cylinder block base 5.

[0029] The apron 2 may be provided with cooling elements 33 on its outer surface in the region of the pannier oil tank 11 to facilitate cooling of oil 16 contained within the pannier oil tank 11. The pannier oil tank 11 of FIG. 1b is also provided with a bottom wall 14. However, in the present embodiment, the bottom wall 14 is formed by the cylinder block base 5.

[0030] Accordingly, the bottom wall valve opening 15 of the pannier oil tank 11 and the fluid passage 38 of FIG. 1b are defined in the cylinder block base 5. The bottom wall valve opening 15 is also openable and closeable by a float valve 17 in the sump 37.

[0031] The pannier oil tank 11 of FIG. 1b, like pannier oil tank 11 of FIG. 1a is adapted to receive oil from a filler tube (not shown) and the cylinder block duct 21 in communication with the cylinder head 8 via the cavity 20 defined between the apron 2 and the cylinder block 1. In the embodiments of both FIGS. 1a and 1 b the cylinder block duct 21 is in communication with the interior of the cylinder head cover 9 via cylinder head ducts 29 provided in the cylinder head 8 itself. The pannier oil tank 11 can also receive oil from miscellaneous sources as described in relation to FIG. 1a.

[0032] The aperture 32 in the crankcase housing 7 also functions to receive crankcase gases from the crankcase 6.

[0033] Both embodiments of the invention are provided with a sump oil pick up 22 located in the sump 37 and an oil pump 23, also housed in the sump 37, for pumping oil from the sump 37 to the crankshaft 10. Oil is directed to the crankshaft 10 by a crankshaft oil feed 25 in communication with the oil pump 23 while the pressure relief oil valve 24 is disposed between the pannier oil tank 11 and the crankshaft oil feed 25. An oil spray (not shown) in communication with the oil pump 23 can also be provided to assist in piston cooling and lubrication of piston pins and rings and the cylinder block side and end walls 35, 36 respectively.

[0034] The lubricating oil is filtered by an oil filter (not shown) to clean the oil and remove debris therefrom in conventional manner.

INDUSTRIAL APPLICABILITY

[0035] The pannier oil tanks 11 of FIGS. 1a and 1 b operate in a similar manner and operation and use of the invention will now be described in relation to a typical six cylinder 6.0 liter engine having a pannier oil tank 11 on each cylinder block side wall 35. However, it will be appreciated by those skilled in the art that the invention finds application in engines having different numbers of cylinders and different capacities while engines can be provided with one, two or more pannier oil tanks 11 as required.

[0036] Lubrication oil 16 from engine main and big end bearings and from piston cooling jets and the like is returned to the sump 37 in a substantially conventional manner.

[0037] Other oil flow from the cylinder head 8, pressure relief valves 24 and engine components including turbo-chargers, camshafts, idler shaft bearings and the like may be returned first to the pannier oil tanks 11 via the cylinder block ducts 21 and the cylinder head ducts 29.

[0038] In the 6.0 liter engine of the present example, the sump 37 is adapted to receive ten liters of oil while the pannier oil tanks 11 are dimensioned to receive six liters of oil before overflowing into the sump 37 through the aperture 32. Maximum oil flow from the pannier oil tanks 11 via bottom wall valve openings 15 is restricted to six or less liters per minute.

[0039] The fluid passage 38 is disposed such that, when open, oil flows under the force of gravity from the pannier oil tank 11 to the sump 37 without the need for an additional pump.

[0040] The float valve 17 is set at a level such that the bottom wall valve opening 15 is open under least favorable operating conditions when oil levels in the sump 37 are at their lowest levels, due to the high volume of oil 16 in circulation in an engine. Accordingly, the float valve 17 is closed under most operating conditions.

[0041] As indicated above, the initial volume of oil is fed, prior to engine start-up, into the pannier oil tank 11 via the filler tube 19. When the oil level in the pannier oil tank reaches the aperture 32 the additional fed oil overflows through the aperture into the sump 37.

[0042] At engine start-up, the pannier oil tanks 11 are full under normal conditions. The float valves 17 are closed due to the high oil level in the sump 37.

[0043] Accordingly, upon engine start up, oil levels in the sump 37 are lowered as oil is pumped around the engine components, enabling the float valve 17 to open to a limited extent.

[0044] At idle speed oil will circulate at a rate which returns 18 liters of oil per minute to the sump 37 and 6.5 liters of oil per minute to the pannier oil tanks 11. If the float valves 17 are closed, and the pannier oil tanks are full, then the 6.5 liters of oil per minute returned to the pannier oil tanks will overflow through the aperture 32 and return to the sump 37. However, under abnormal conditions where the float valves 17 are open, then assuming the float valves 17 are fully opened and sized to permit a flow of 6 liters of oil per minute, the pannier oil tanks 11 are filled approximately 12 minutes after start up, based on a net flow of 0.5 liters of oil per minute into the pannier oil tanks.

[0045] In practice, the float valves 17 are generally completely shut due to high oil levels 16 in the sump 37 so that the pannier oil tanks 11 fill at a faster rate.

[0046] At most engine operating regimes, flow rate of oil returned to the pannier oil tanks 11 greatly exceeds flow rate from the pannier oil tanks 11. Flow rates are calibrated such that, at idle speeds, oil in circulation is insufficient to allow oil levels in the sump 37 to depress to the point where the valves 17 will open. As previously described, any overflow from the pannier oil tanks 11 through the apertures 32 simply enters circulation in the engine. At running speeds, oil levels in the sump 37 are further depressed due to the increased volume of oil in circulation whereby the float valves 17 may open. Opening of the float valves 17 in such a manner therefore results in a stabilization of oil levels in the pannier oil tanks 11 at a level proportionate to return flow of the oil 16.

[0047] Oil within the pannier oil tanks 11 is also cooled in the embodiment described in FIG. 1b due to the cooling elements 33.

[0048] In short, oil level within the sump 37 is regulated to be at a correct level in accordance with engine requirements at all times due to the presence of the pannier oil tanks 11 and the co-operation of the bottom wall valve openings 15 and float valves 17.

[0049] Table 1 below summarizes the above described oil flows in an engine: TABLE 1 Typical Oil Flows Peak Torque/ Idle Cruise Rated Speed Litre/min % Litre/min % Litre/min % Speed - rpm 700 1500 2200 Bearings 17 32 47 Cooling Jet 1 8 13 Return to sump 18 73% 40 44.1% 60 47.3% Turbo 3 4.2 4.5 Relief valve 0 30 40 Head/valve gear 1 2 2 Bypass filter 1 8 11.5 Miscellaneous 1.5 6.4 8.7 Return to pannier 6.5 27% 50.6 55.9% 66.7 52.7% oil tanks (11) Total flow 24.5 100%  90.6  100% 126.7  100%

[0050] As indicated above, where the engine is running the volume of oil 16 in circulation results in oil levels in the sump 37 being lowered so that the float valves 17 are partially opened. However, when the engine is stopped, oil in circulation within the engine is returned to the sump 37 and the pannier oil tanks 11 in proportions relative to the engine operating speed immediately prior to shut down. The float valves 17 remain open until the sump 37 is at least partially filed with oil 16. In practice, return of oil 16 to the sump 37 occurs in advance of return of oil 16 to the pannier oil tanks 11 due to longer return paths from pannier oil tank filling sources, such as the cylinder head 8. When the float valves 17 are closed, the oil level in the sump 37 continues to rise to a normal level due to the large volume of sump return oil 16 in circulation.

[0051] When servicing the engine, oil drain may be achieved through a sump plug or a suction tube into the sump 37. At a critical drainage level, the float valves 17 are opened thereby permitting the pannier oil tanks 11 also to drain.

[0052] On refilling, the pannier oil tanks 11 are filled through the filler tube 19 and hence the sump 37 becomes filled via the bottom wall valve opening 15. If an excessive filling rate is used, the oil tank panniers 11 simply overflow into the sump 37 via the apertures 32 as previously described.

[0053] The invention finds application in engines where it is desired to incorporate an oil capacitor to supplement the oil sump without detriment to engine servicing efficiency and without compromising oil cleanliness and durability within the engine during operation.

[0054] The invention is not limited to the embodiments herein before described which may be varied in both construction and detail. 

What is claimed is:
 1. A cylinder block assembly comprising a cylinder block, a primary lubricant reservoir below the cylinder block, a secondary lubricant reservoir at a side of the cylinder block, a fluid passage extending between the primary and secondary lubricant reservoirs, and a valve that can be actuated to open and close the fluid passage, wherein the fluid passage is adapted to permit gravitational flow of the lubricant from the secondary lubricant reservoir to the primary lubricant reservoir when open, wherein actuation of the valve is controlled by a level of lubricant in the primary lubricant reservoir.
 2. A cylinder block assembly as set forth in claim 1, wherein the valve is a float valve.
 3. A cylinder block as set forth in claim 1, wherein the fluid passage comprises an aperture in the secondary lubricant reservoir.
 4. A cylinder block assembly as set forth in claim 1, further including a cylinder head and a cylinder head cover on the cylinder head, wherein the secondary lubricant reservoir communicates at least one duct with an interior of the cylinder head cover.
 5. A cylinder block assembly as set forth in claim 5, wherein the valve is a float valve.
 6. A cylinder block assembly as set forth in claim 1, further including a crankcase above the primary lubricant reservoir, wherein the secondary lubricant reservoir is provided with an overflow aperture in a side wall thereof communicable with the crankcase.
 7. A cylinder block assembly as set forth in claim 1, further including a crankcase above the primary lubricant reservoir, wherein the secondary lubricant reservoir is provided with an overflow aperture in a side wall thereof communicable with the crankcase.
 8. A cylinder block assembly as set forth in claim 1, wherein the secondary lubricant reservoir is defined between a wall of the cylinder block and an apron sealably mounted on the cylinder block.
 9. A cylinder block assembly as set forth in claim 8, wherein the valve is a float valve.
 10. A cylinder block assembly as set forth in claim 4, wherein the secondary lubricant reservoir is defined between a wall of the cylinder block and an apron sealably mounted on the cylinder block.
 11. A cylinder block assembly as set forth in claim 10, wherein the valve is a float valve.
 12. A cylinder block assembly as claimed in claim 1, wherein the secondary lubricant reservoir is defined between an outer wall and an inner wall of the cylinder block.
 13. A cylinder block assembly as set forth in claim 14, wherein the valve is a float valve.
 14. A cylinder block assembly as set forth in claim 1, wherein the secondary lubricant reservoir is defined between an outer wall and an inner wall of the cylinder block.
 15. A cylinder block assembly as set forth in claim 16, wherein the valve is a float valve.
 16. A cylinder block assembly as set forth in claim 1, wherein said valve is actuated to close the fluid passage when the lubricant level in the primary lubricant reservoir is above a predetermined level, and wherein said valve is actuated to open the fluid passage when the lubricant level in the primary lubricant reservoir is below the predetermined level.
 17. A cylinder block assembly comprising a cylinder block, a primary lubricant reservoir below the cylinder block, a secondary lubricant reservoir at a side of the cylinder block, a fluid passage extending between the primary and secondary lubricant reservoirs, and a valve that can be actuated to open and close the fluid passage, wherein the fluid passage is adapted to permit gravitational flow of the lubricant from the secondary lubricant reservoir to the primary lubricant reservoir when open, wherein said valve is actuated to close the fluid passage when the lubricant level in the primary lubricant reservoir is above a predetermined level, and wherein said valve is actuated to open the fluid passage when the lubricant level in the primary lubricant reservoir is below the predetermined level.
 18. An engine comprising a cylinder block assembly and a cylinder head mounted to said cylinder block assembly, wherein said cylinder block assembly comprises a cylinder block assembly as set forth in claim
 1. 19. A method for lubricating an engine having a cylinder block, a primary lubricant reservoir below the cylinder block and a secondary lubricant reservoir, comprising the steps of: pumping lubricant around the engine from the primary lubricant reservoir; collecting a proportion of returned lubricant in the secondary lubricant reservoir; and controlling the return of lubricant from the secondary lubricant reservoir under gravity to the primary lubricant reservoir.
 20. A method as set forth in claim 19, wherein the return of lubricant from the secondary lubricant reservoir to the primary lubricant reservoir is controlled by a float valve, such that return of lubricant is prevented when the lubricant level in the primary lubricant reservoir is above a predetermined level, and return of lubricant is allowed when the lubricant level in the primary lubricant reservoir is below the predetermined level. 